Variable pitch propeller mechanism



Feb. 24, 1942. w s. HOOVER VARIABLE PIT CH PBOPELLER MECHANISM asheets-sheet 1 Original Filed Nov. 2'7, 1934 Feb. 24, 1942. w. s. HOOVER22,034

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VARIABLE PITCH PROPELLER MECHANISM- 8 Sheets-Sheet 6 Original Filed Nov.27, 1954 lnuemfor, h d/fer 6'. H00 very" Feb. 24,1942.

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w. s. HOOVER Re. 22,034 VARIABLE PITCH PROPELLER MECHANISM OriginalFiled Nov. 27, 19:54

8 Sheets-Sheet 8 6/ l a? 4Z1 [nae/1731", WEI/fer 6. Hoover? r Him/mgRei'a'ued Eeb. 24, 1942 UNITED STATES] PATENTF'QFFICE VARIABLE PITCHPROPELLER. MECHANISM Walter's. Hoover, West Hartford, Conn. Original No.2,184,143, dated December 19, 1939,

Serial No. 755,031, November 27, 1934.

newed September 15, 1936..

Re- Application for reissue July 27, 1940, Serial No. 348,011

13 Claims.

This invention relates to improvements in variable pitch propellermechanism, of the general type disclosed in my Patent 1,972,486, issuedSeptember 4, 1934.

In the aforementioned patent there is disclosed anhydraulic mechanismfor manually and/or automatically effecting the pitch setting of thepropeller blades in accordance with the motor load conditions incidentto the maneuverability of air-craft.

In accordance with the present invention,"

novel means are provided for transmitting the force developed by thehydraulic unit to' the propeller blades in a manner to prevent huntingof the motor which is characteristic of the automatically controlledvariable pitch propeller mechanisms heretofore proposed.

In accordance with the present invention, the medium through which'thehydraulic force is transmitted is self-locking and yet eliminatesfriction loss, thus rendering it'highly emcient and in addition providesa high reduction ratio between the source of power and the blades.

It is another object of the invention to provide mechanism which shallbe adapted to effect a change in the setting of the propeller pitchangle in a smooth and steady manner thereby preventing abrupt changes inmotor operation and consequent severestress on the operating parts.

Still another object ofthe invention is the provision of semi-automaticmeans for manually controlling the adjustment for pitch setting throughthe medium of electrical control of, the hydraulic unit which, whenreleased, restores automatic control. T

Still a further object of the invention is the provision of manualcontrol means for the hyportion of the propeller hub unit illustrating amodified form of hydraulic rotor;

- Fig. 6a rear view with the housing shown in Fig. 5 partly cut away;

Fig. 7 a plan view of the blade operating an'-' nulus diagrammaticallyillustrating the mounting of the internal counterweights on the blades;

Fig. 8 a cross-sectional view partially in elevation of anelectro-magnetically actuated control valve;

Fig. 9a plan view of the pressure and relief tubes with control valveand governor arms;

Fig. 10 a cross-section of the tube of Fig. 9

taken on line l0lll, Fig. 9;

routing of, the pressure fluid through the con- 'the propeller bladeanchorages.

purpose of illustration a hub design for twov Fig. 11 a plan view of theroller bearing for the blade anchorage shown in Fig. 3;

Fig. 12 a diagrammatic showing of the oil pres-'- sure system and itsconnection to the engine and pitch adjusting unit; and

Fig. 13 a diagrammatic view illustrating the trol valve to the hydraulicactuating unit.

With reference to Figs. 1 to 4 inclusive of the drawings, the numeral Igenerally designates a propeller hub casting or forging havingoppositely disposed hollow extensions 2 for mounting While for theblades is shown, it is obvious that the invention is applicable topropeller mountings employing any number of adjustable blades.

draulic operating mechanism which may be readily substituted for thefully automatic or semi-automatic control mechanism..- These and otherobjects of the invention will become more apparent from a-considerationof the accompanying drawings constituting a part hereof in which likereference characters desig- ,nate like parts and in which: Fig. l is afront elevational view of' a variable pitch prop'ellen unit embodyingthe principles of this invention, having its front cover removed;

Fig. 2 a cross-sectional view thereof taken along the line 2-1, Fig. l;Fig. 3 a side elevaticnal view partially in sec-.

tion of the structure shown in Figs. 1 and 2;

, Fig. 4 a sectional elevational view taken on the line 4-4, 'Fig. 3; I

Fig. 5 a side elevation partially in section of a In Fig. 3 the bladeroot 3 is shown provided with a buttress thread 4 to receive an annulus5 on which is mounted oppositely disposed counterweights 6, thecounterweightsbeing at right angles to the face of the blades as isdiagram-.

matically shown in Fig. '7 of the drawings. The function of thecounterweights- 6 is to partly counter-balance the magnitudes ofcentrifugal torsion moments which act on the geometrical mass of theblade to assume lines of exact radii from the nearest centerline tendingto flattenout th pitch in the plane of rotation. For

example, in a propeller operating at 2,100" R. P.

M. with the centrifugal torsion at about 4,000 inch pounds for eachblade, the employment of internal counterweights 6, while ineffective toentirely balance-out the centrifugal torsion because of spacelimitations, will reduce the magnitude of centrifugal torsion momentsabout 1,500 inch pounds for each blade. 7 The weights are positioned atapproximately from the crank shaft centerline when the bladesareadjusted for normaloperation'.

A sleeve 1, Fig. 3, having a flange 8 houses a series of roller bearings9 and Ill, the'bearings .9 having their axes parallel to the axis of the-blade to take up the angular thrust of the blade, and the remainingbearings III are radially dis-' posed to take up the centrifugal thrustof the blade. Roller bearings II are provided at the extreme lower endof the blade root with theirwith an annular lead 39 having portedopenings 39. The pressure is released through a duplicate annular lead38a communicating with the ported'opening 40, the annular leads beingmore axes in parallel;.alinement with the bearings 9 to take up theangular thrust and to provide a maximum spacing of the thrust bearingsto provide strength and rigidity invariable propeller blade mounting.The bearings II by their manner of assembly are preloaded to take upinternal slackness of the bearing set up. The bearings Ill areinterchangeable and are necessarily designed to effect uniformdistribution of the load on all of the thrust members, the roller racesrequiring precision in their tolerances. The short leg of the L-shapedraces is adapted to flex slightly under load to make up anydiscrepancies in the tolerances of successive bearings, thus equalizingthe load over a series of stack bearings.

, The propeller blade anchorages as above de scribed are actuated tovary the pitch setting by subjecting the annulus 5 in which they are l5,one of which fits into a hemisphericalseat in the projecting portion l4,and the other ball is held in place by an adjustable cavity in a screwit.

The worm I2 is mounted on a shaft I! having a pinion l3 that interactswith the teeth of a ring gear l9 which is actuated by a fluidmotorgenerally designated by the numeral 20.

The worm shaft l l isanti-frictionally mounted by bearings 2| and 22,and a U-shape packing 23 prevents leakage of fluid from the hydraulicunit through the gear teeth.

The hydraulic unit 20 comprises a rotor 24 having flanges '25 and 26which in cooperation with housing walls 21 and 28 form leak pressurecavities 29 and 30, the flange-walls and 26 being of rigid mechanicalconstruction to prevent distortion and to permit of proper sealing ofthe housing and rotor by gaskets 2|. The, leak pressure cavities 29 and.30 are adapted to counteract the internal pressure of the rotor bybuilding clearly shown in'Fig. 2.

The flow. of fluid is controlled through valve mechanism generallydesignated by the numeral 4| which regulates the flow from a port 42 inthe side of the propeller hub shaft, Fig. 2, to a flow cavity 43 whichsurrounds arelief pipe 44 by which the fluid is returned to the pressuresource. The flow cavity 43 communicates with a tube 45 that extends to'a .valve chamber 45, Fig. 3, from which it flows through a portedpassage 48 to thepressure lead 31 of the rotor, Figs. 2 and 4.

Ported passages 48 and 48a are controlled by a slide valve 49, Figs. 3,8 and 10, the valve being of spool shape and hollow in the center tobalance the pressure on its outer flange. Valve 49 is actuated by agovernor to control the flow of pressure to one side of the vanes 33 andsimultaneously relieve the pressure on the opposite side. The governorcomprises shafts 50 having governor arms 5I,,Figs. 1 and 3, which areresponsive to centrifugal force producedby rotation of the hub toactuate their respective shafts 5!! which bring about the movement ofthe slide or spool valve 49 throughzconnecting levers 50c, Figs.3, 8 and10. It will be apparent from Fig. 3

. that when'valve 49 is moved in the direction where it uncovers theport 43 on the outside of its end flange, it will simultaneously uncoverthe other port 43a on the inside of the opposite flange (Fig. 3)thus'relieving the pressure on one side of vane 33 through the passage41 of the inner tube or pipe 44. Q

Valve 49 is controllable manually for synchronizing the pitch setting ofa plurality of propeller units by actuating'governor arms 5|independently of the centrifugal force that tends'to spread them, such"control being effected through a pair of electrical solenoids 52, Fig.1, and solenoids 57 and 58, Fig 8, that are electrically connectedthrough lead wires 53 with collector rings 54 mounted on the rear of thehydraulic rotor, current being supplied to the collector ring throughbrushes 55 connected 'to a source of electrical energy such as abattery. The control is effected by means. of a push button switch- (notshown) which, when held depressed by the operator, will energizesolenoids 52 thereby drawing out the governor arms 5| to produce thedesirable adjustment of the valve 49 thatcauses up pressure due to theslippage of fluid by the- I pressure differential between the inner andouter faces of the flanged wall. The pressure on both sides of theflanged walls 25 and 28 is substantially balanced by the leak pressurebalancing leaks 32 extending through movable vanes 33 and through flangewalls 25 and 26, this lead being shown in dotted lines in Fig. 2 and ismore clearly shown in Fig. 4 of the drawings.

With reference to Fig. 4, the hydraulic unit embodies a pair ofstationary abutments 34 which are secured to the housing 21 by cap bolts35 or in any other suitable manner, these stationary abutmentscooperating with the movable vanes 33 that are attached by dowel pins35..to the flange walls 25 and 25 of the rotor, the vanes 33 cooperatingwith the fixed abutments to be relatively movable by fluid presure whichis supplied through a pressure lead 31 communicating actuation ofthemovable vanes of the hydraulic unit to produce a desirable pitchsetting. When the button switch is released, solenoids 52 will bedeenergized and governor arms II will assume the position they wouldhave for the particular revolutions of the propeller shaft at the timeof such release.

The mechanism may also be entirely manually I controlled bymeans of thestructure shown in- Fig. 8 wherein the governor arms 5! are removed fromtheir shafts 53 and a movable armature 5G is mounted on one-of saidshafts. The armature' is actuated by solenoids 51 and 59 which are wiredto collector rings 54, Fig. 3, and controlled by separate switches. Thevalve 49 shown I in Fig. 8 is biased by cofl springs 59 to a normalposition o1 pitch setting. Valve 49 is provided with an axiallyextending finger 5la having a notch 49b which is engaged by a lever 50amounted to be movable with shaft 53 in response to angular movement ofthe armature 56. It will be noted as viewed in Fig. 8 of the drawingsthat the valve 49 has flanged ends which control the ported ducts and49a for directing the fluid pressure to the hydraulic actuator foreffecting a forward or reverse pitch setting, the

with one of the switches the valve 49 will route the actuating fluid toset the pitch of the blades to forward position, and by energizing theother of the solenoids the fluid will be routed to reverse the pitchsetting 01 the blade thus affording an all-manual control without anychange of the blade actuating mechanism.

A modified form of hydraulic unit or motor is shownin Figs 5 and 6 ofthe drawings, and consists of a movable housing member which carries themovable vanes 8 I that cooperate with 's't'a'tionary abutments 62secured to a sleeve 63 by bolts 63a. Sleeve 63 is keyed to a stationaryhub portion 63 by a key 64, Fig. 5. The numeral 64a designates anannular pressure lead having ported openings therein. The operation ofthis type in which the outer housing is movable instead of the innerpart as in Fig. 4, is thesame as that of the operation of the structureof Fig. 4, the fluid pressure and relief passages being the same as isreadily apparent from comparison of the two figures, the primary aim'ofthe cylinder housing being to prevent distortion due to the oilpressures used. v L

Fig. 9 shows in detail the relief tube 44 and the pressure tube 45, oneend of the relief tube a 44 being provided with'a plug that fits in thecounterbored portion of the propeller hub shaft 66, a screw plug 61interacting with threads provided in the end of shaft 66 to hold thesupply tubes 44 and 45 in position.

The pressure tube 45 has a threaded portion 68 that cooperateswithU-shaped leather packing for longitudinal adiustmentwi h the tapered,face of crank shaft 58 with which it seals, and

a screw plug 69 is provided to render valve 49 accessible. jGovemor arms5| are shown .at-- tached to theendof the tube-like structure and areoperatively connected to valve 49 to adjust the latter in response tovariation in the motor *speeds. I T

Fig. l2 diagrammatically illustrates a system for the development of oilpressure in a-,con v entional motor bythe' .use of'auxiliary equipmentwhich functions to'de-velop pressure in excess of the engine pressureswhile maintaining lower pressure on the oil used for lubricating the emI gine parts,. In Fig. 12'the numeral 69 designates. a gear pump havinga conduit Ill. leading :to a

' maintank I l.. and aconduit 12 thatde'livers flu id is j,distributedathigh pressure'througih'c d "to the hydraulic propeller'unit genera hated by fthenumeral l5 Pump-1B9, 'de 'oil to chamber,13 ata pressure-in eircess [maximum pressure required for "scent I hydraulicpropeller unit, and chamber-1i v vided with a relief :'valve 13a havingadjustable means for setting the valve to maintain ,pre-

determined oil pressure in chamber 13 is; for

-- example, 209 pounds. so thatthe pressure ole-'- liveredthrougli""'conduits 14 to the hydraulic pitch setting unitwill always,be at 200 pounds,

or whatever pressure is desired. Thebalance of the fluid delivered bypump 69 passes from chamber 19 through conduit 13b to a chamber 130which is provided with a relief or blow-oil valve 5 13d to maintain apredetermined pressure, such as 75 pounds, in the tank 130. Thelubricating fluid is delivered to the engine by conduit 136 from chamber13c and the fluid, after passing through the parts of the engine to belubricated, m is returned to the engine sump 18, the blow-off and leakfrom chamber 130 and the engine being shown by dot-and-dash lines. Thedrain or return flow from the hydraulic propeller unit is shown aspassing out the off-set of the crank 15 shaft at the portion designatedby the numeral 11. The oil from the engine sump is returned to thescavenging side 89 of pump 69 which returns it to the main tank H.

The operation of the above described variable go pitch propellermechanism is briefly as follows:

Assuming the blade roots to be'mounted for rotary movement ashereinabove described, that is, in the bearing set up shown in Fig. 3with the counterweighted annuli 5 in cooperative engage- 'ment with theworms I! through rollers i3, the pitch of the propeller blades in theabsence of manual control will be entirely determined by the operationof the governor arms 5| which respond to the centrifugal force producedby the :m speeds of the motor. As the governor arms 5| I move angularlyon their shafts 50, the valve 49 controlling theflow of fluid underpressure to the rotary abutments of the hydraulic unit will beactuatedby levers 50a, Fig. 13, to open and :15 close the ported passages 48 and48a, respectively, thereby routing .the pressure fluid from passages 41and 41a through port 48 to the pressure lead 31 of the rotor therebysubjecting the movable vanes 'or abutments of the hydraulic unit in topressureon one side and relieving the'pre'ssure on the opposite sidethrough port 49a to the '!'sump passage 4|, causing the rotor po tion 33I to rotate which, through ring gear I9, actuates pinion l8 andconnected worm shaft l2 causing the annuli 5-to move angularly to effectthe change in pitch setting; i

As previously stated, the worm drive is a selflocking device which:prevents hunting of the motor due to leakage-of pressure or slippage of:m the mechanical linkage, and yetthrough the roll-- er engagement urineworm with the annuli substantially all frictiomis eliminated. Further,by

' means of the worm drive, a high reduction ratio between-the fanv bladeand hydraulic rotor is 5 attainable so that excessive fluid pressuresare not required to operate the-pitch setting mechaisms. I

In the modification 'of hydrau ic unit shown 7 Figs. 5 and 6, the sameprinciple of operation no is present, the l only difference in theconstrucmen being the rotary movement of the housing instead of theinner member. If it is desirable to use the "manual control as instarting. the cperator e'nergiies the circuit of solenoids 52' which f-actuate the governor arms 51 to effect a change of setting of valve '49and a. consequent movement of the rotary abutments to change the pitchangle. r 7 When the .fnanua-l control switch 'is released, thesolenoids-filwill be 'deenergized and governor 1 arms 51 willjf bereleased to the position which i'they would normallygassume for theparticular 4 engine speed at such time. If the all-manual control isemployed as in the tion of pressure to the face of the movable vanes.

One of the solenoids will move the valve actuat-.

'ing armature 56 to forward position of pitch setting and the other toreverse pitch setting, and

. when both electrical circuits are deenergized, the

valve will assume the position in which the blades will be disposed fora given operating condition.

speed responsive device to actuate the rotor in accordance with desiredchanges in the pitch setting of the blade anchorage members.

3. A hydraulic unit for changing the pitch setting of variable pitchpropeller blades comprising a hub structure, a plurality ofv bladeanchor- In the exercise of the manual control the solenoid circuits willremain energized only so long as the operator makes contact with pushbutton or other control switch.

It is apparent from the foregoing description of this invention thatvariable pitch propeller mechanism operating on the hydraulic principleand embodying the principles herein disclosed provide eflicient meansfor propeller blade adjustment within a compact space with-mechanicaldevices that are compact and not of excessive weight.

By mounting the hydraulic unit or rotor at the rear of the hub morecompactness and a shorter design is obtainable.

Although one embodiment of the invention has been herein illustrated anddescribed, it will be obvious to those skilled in the art that variousmodifications may be made in the details of construction and in thearrangement of the coop-.

crating parts without departing from the principles herein set forth.

I claim:

l. A hydraulic unit controlling the pitch setting of variable pitchpropeller blades comprising a hub structure, blade anchorages mountedtherein, a double acting vane type hydraulic actuator operativelyconnected to the blade anchorages to render them simultaneously movable,said actuator communicating with a source of fluid pres-. sure, valvemeans controlling the application of fluid pressure to said actuator,said means being normally biased to maintain the valve in one positionof its operation, electro-magnetic means age members rotatably mountedtherein, a double acting vane type hydraulic actuator geared to theblade anchorages to render them simultaneousl'y movable, a conduit forsupplying fluid pressure to said hydraulic actuator from a source remotefrom said propeller, valve means for controlling the application offluid pressure to said actuator, means foroperating the control valvecomprising a movable armature normally biased to maintain the valve inoneposition of its operation, electromagnetic actuating means for saidarmature, said valve, armature and electromagnetic means being carriedbysaid' hub structure, and meansfor selectively energizing saidelectromagnetic means to increase or decrease the pitch settingof theblades comprising, electrical contacts movable with said hub andelectrically-connected to said electromagnetic'means, and means forsupplying a source of electrical energy to said movable contacts.

4. A variable pitch propeller mechanism comprising a hub structure andblades movably mounted therein, a double-acting vaned type of neticmeans for actuating said valve, said means comprising electricalcontacts movable with said for moving said valve means in the otherPositions of its operation, said valve and electromagnetic means beingcarried by said hub structure and means for energizing saidelectromagnetic means to render said valve means operative'to increaseor decrease the pitch setting of the propeller blades. comprising,electrical contacts movable with said hub and electrically connected tosaid electromagnetic means, and means for supplying a source ofelectrical energy to said movable contacts.

2. A variable pitch propeller mechanism comprising a hub structure,blade anchorages mounted ior rotary movement therein, screw shaftshaving gear tooth engagement with said anchorages, fluid pressuremechanism for simultaneously actuating the screw shafts and controlmeans for said fluid pressure mechanism mounted in said hub androtatable therewith to adjust the pitch setting of the blade anchoragesin response to the speed of the hub, said fluid pressure mechanismcomprising a housing having a plurality o1 sta-.

tionary abutments, and a rotor having movable abutments, said rotorbeing gearedto the screw shafts and said control means consisting of aspeed responsive device and a slide valve connected to a source of fluidpressure andto'the space between the stationary and movable abutments,said slide valve being actuated bythe hub and electrically connected tosaid electro-' magnetic means, and means for supplying a source ofelectrical energy to said movable con tacts. i

5. A variable pitch propeller mechanism comprising a hub structure andblades movably mounted therein, a double-acting vaned type of fluidmotor, mounted on the propeller hub, connected with the blades forchanging the pitch of the blades, a conduit for supplying fluid underpressure to said motor from a source remote from said hub, a valve insaid hub'contro'lling the application of said fluid to actuatesaidmotor, electromagnetic means for actuating-said valve, contact ringson said hub, stationary brushes in constant engagement with-said ringsand connected to a, source of electrical energy, and electricalconduits. connecting said rings and electro-magnetic valve actuatingmeans.

6. A variable pitch propeller mechanism comprising a hub structure andblades movably mounted therein,- a fluid motor mounted on the propellerhub connected with the blades for changing the pitch of theblades, aconduit for supplying fluid under pressure to said motor from a. sourceremote from said hub, a valve in said hub controlling the application ofsaid fluid to actuate said motor, a. governor having movable weightsmounted in and rotatable with said hub structure, said weights 'beingresponsive to the speed of the propeller hub to actuate saidfluidcontrolling valve,- electromagnetic means for actuating thegovernor-weights to actuate the fluid control valveat the will of theoperator, said electromagnetic means having electrical connection with acurrent collecting means mounted on.

the hubstructure and rotatable therewith, and

means for supplying a source or electrical energy to said currentcollecting means.

7. In combination with a controllable pitch propeller having a range ofpitch adjustment between fixed limit stops, hydraulic means for changingthe pitch of said propeller, a valve rotatable with the propellercontrolling said hydraulic means, a governor responsive to the speed ofthe propeller for actuating said valve in one direction, a spring foractuating said valve in up position to said governor, and manuallycontrolled means rotatable with said propeller, said valve having aneutral position in which said valve is under the control of saidgovernor and said spring, said manually controlled means acting uponsaid value to positively move said valve to a fixed pitch settingposition against the action of said govemor and said spring;

a. In combination with a controllable pitch propeller having a range ofpitch adjustment between fixed limit stops, hydraulic means for changingthe pitch of said propeller, a valve ro-, -tatable with the propellercontrolling said hydraulic means, a governor responsive to the speed ofthe propeller for actuating said valve in one direction, a spring foractuating said valve in opposition to said governor, and electromagneticmeans rotatable with the propeller operable to hold said valve in afixed position of its pitch setting movement independently of the actionof said governor and said spring.

9. In combination with a controllable pitch propeller having a range ofpitch adjustment between flxed limit stops, hydraulic means for changingthe pitchot said propeller, a valve rotatable with the propellercontrolling said hy draulic means, a governor responsive to the speed ofthe propeller for actuating said valve in one direction, a spring foractuating said valve in opposition to said governor, and electromagneticmeans rotatable with the propeller operable to actuate the governor armsand control valve independently of the speed of the motor.

said high and low pitch setting, a control valve rotatable with saidpropeller for said actuating means, governor means responsive to thepropeller speed for controlling said valve, spring means biasing thespeed responsive elements of the governor means, and electromagneticmeans rotata'ble with said propeller for operating said governor speedresponsive elements independently of the propeller speed.

11. In a variable pitch propeller, propeller-blade pitch-changingmechanism comprising a rotary hydraulically-actuated angularly-movabledisplacement means geared to the blades of said' propeller, a spoolvalve hollow throughout its length and subject to equal fiuid pressureat each end located in said propeller with the axis of said valvedisposed transversely to the axis of the-propeller, said valvecontrolling the flow of engine lubricating .fiuid to and from saidmechanism for operating the same, and speed responsive means in saidpropeller operatively conan electromagnetic force acting upon the metalof the'governor fly-weights for operating said governor independently ofthe propeller speed.

13. In combination with a controllable pitch propeller having a hubstructure, a plurality of pressure communicating with said valve, agov-- ernor ior said valve rotatable with the propeller, electromagneticmeans for controlling said valve at the will of the operator, and aninternal mass rotatable with the propeller developing a forcecounterbalancing the centrifugal moment of the blades.

\ WALTER S. HOOVER.

